LightUp v2.7b

This release has quite a few bug fixes and performance improvements.
- faster processing emitters
- improved accuracy of energy transfer in AO
- fix for LightMeterSample label scaling
- fix for freeze on some Mac graphics cards
- faster skybox generation
- fix for saving/loading IOR to .luca
- filter out punctuation in export FBX names
- margin around layout of LightMeterGrids
- Right-click for No Backface Cull flag
- Change Skybox without restarting TourTool.
- Menu for manual override to use GLSL
- Cutoff could set to 1.0 showing no reflections
- Fixed IrrCache binding bug

Updated Player and WebPlayers